"It was never diagnosed and doctors were baffled," said Jennifer Horsley. "I don't think they had even heard the name."
Methemoglobinemia may be passed down through families or can be caused by exposure to certain drugs, chemicals or foods.
In Green's case, the disorder was genetic and occurs when there is a problem with the enzyme called cytochrome b5 reductase.
In type one, the red blood cells lack the enzyme. In type 2 -- also called hemoglobin M disease -- the enzyme doesn't work anywhere in the body.
Green has M disease, which is caused by defects in the hemoglobin molecule itself and can be passed down from only one parent.
The disorder once saved his father's life, according to a story told by Green's mother. "A woman shot him five times and he didn't bleed out because his blood was so thick."
For that very reason, Green takes three different blood-thinning drugs to prevent blood clots and morphine for the pain.
"I have found a way to live around it the best I can," he said. "It's caused me a lot of emotional problems.
As for finding his father, "I would really like to know more about how he grew up with it and how he dealt with it. My father and I never met, but come to find out, we are a lot alike."